Devices that record on or reproduce from disk-shaped recording media, such as optical disk devices for a CD (compact disk), DVD (digital versatile disk), BD (Blu-ray disk), or the like, or magneto-optical disk devices for an MO (magneto-optical disk), MD (mini-disk), or the like, or recording and reproduction magnetic disk devices for an FD (floppy (registered trademark) disk) or the like, and the various disk media used in these devices have already gained widespread acceptance in the world.
Furthermore, technology aimed at increasing recording density is proceeding at a rapid pace today, and this progress brings with it the need for higher precision in the above-mentioned disk devices. In particular, the highest precision is required of the heads acting directly on recording or reproduction on disks.
Meanwhile, the price of these disk devices continues to drop in the marketplace, and the parts, materials, and methods used to make these devices need to be inexpensive yet highly functional.
Also, from the standpoint of lowering transportation costs at the same time, the ideal packaging used to ship these devices is one that is as simple as possible. Reducing the cushioning material used to protect packaged devices has therefore become a goal. The trend today is also toward limiting the use of foamed resins, which are effective as materials used for cushioning, in the viewpoint of environmental protection.
Because the above-mentioned disk devices are thus becoming increasingly precise while fewer options are available for protecting the finished products, either the product strength needs to be increased, or the product itself needs to be capable of protecting its own weak points.
For instance, with an optical disk device that performs recording or reproduction by directing light beam from an optical head at an optical disk that is rotated by a rotation mechanism, the optical head is made up of many optical parts that need to have high precision. Although increasing the joint strength of parts or increasing the part strength itself is one way in order to maintain the precision even after the device has been subjected to an impact or other excessive external force, this often leads to higher unit part prices or more labor in joining the parts. In view of this, it is effective to employ a method that avoids subjecting the optical head to such impact force.
An example of a conventional optical disk device will now be described through reference to FIGS. 16 to 18. The structures of the device have been disclosed in Japanese Laid-Open Patent Application H10-74370, for example.
The optical head in an optical disk device is generally guided and moved in a radial direction of the disk. If it is subjected to an impact force in this movement direction, the optical head may be forcibly moved to the inside or outside in the radial direction and hit the base member, or a part integrally supported by the base member, at the stop position at the movement range limit. This subjects the optical head to a tremendous impact force. This can cause damages that directly and adversely affects performance of the device, such as damaging the internal parts that make up the optical head, reducing the positional precision between the constituent parts and the like.
FIG. 16 is an example of the mechanism for recording or reproducing with a conventional disk device. In FIG. 16, 33 is a spindle motor for rotationally driving a disk 31. The spindle motor 33 includes a turntable on which the disk 31 is placed and fixed. A chucking member for fixing the disk 31 is not shown in FIG. 16, 34 is an optical head that emits a light beam, 35A and 35B are guide shafts for guiding the optical head 34 in the radial direction of the disk placed on the turntable, 37A, 37B, 37C, and 37D are bearings that support the guide shafts 35A and 35B, 39 is a movement motor that serves as a drive source for moving the optical head 34 in the radial direction of the disk placed on the turntable, 38 is a lead screw comprising a spiral groove provided around the peripheral face of a shaft thereof and which is rotated by the drive force of the movement motor 39, 41 is a transmission member unit that engages with the lead screw 38 and transmits a propulsion force that moves the optical head 34 in the disk radial direction, and 32 is a chassis that integrally supports the above-mentioned members. 32A and 32B are an inner peripheral stopper and outer peripheral stopper, respectively, for limiting the movement of the optical head 34 at the disk innermost peripheral location and outermost peripheral location, respectively. The optical head 34 comes into contact with the inner peripheral stopper 32A and the outer peripheral stopper 32B at the innermost peripheral location and outermost peripheral location, respectively.
FIG. 17 is a detail diagram of the portion in which the transmission member unit 41 in FIG. 16 is fixed to the optical head 34 and engages with the lead screw 38 shown in FIG. 18. In FIG. 17, 43 is a tooth component that engages with the spiral groove provided around the axial peripheral face of the lead screw 38, and is supported by an elastic support member 42. 44 is a compression spring for biasing the tooth component 43 toward the lead screw 38, and 46 is a tooth component thrust limiting member for limiting the position of the tooth component 43 with respect to the axial direction of the lead screw 38. The tooth component thrust limiting member 46 is disposed with a specific gap between itself and the tooth component 43. These members are integrally constituted on an attachment base 45 and fixed and supported by the optical head 34.
With the configurations in FIGS. 16 and 17, the optical head 34 is moved in the radial direction of the disk 31 by driving the movement motor 39, and recording or reproduction is performed at a specific radial position of the disk 31.
FIG. 18 is a diagram of the detailed structure of the engagement portion between the tooth component 43 and the lead screw 38 as seen in the direction of the arrow PJ2 in FIG. 17. As shown in FIG. 18, when the lead screw 38 turns in the direction of the arrow R11, the tooth component 43 is subjected to moment in the direction of the arrows D11 and D13. At this point, the optical head 34 is subjected to force from the tooth component 43 via the attachment base 45 and the elastic support member 42, and is subjected to force in the D12 direction. Thus, the optical head 34 obtains a propulsion force in the radial direction of the disk. At the same time, the tooth faces of the tooth component 43 are subjected to force in the direction away from the lead screw 38, but this is blocked by the biasing force of the compression spring 44.
However, when excessive drive force is produced by the lead screw 38 due, for example, to a loss of control of the movement motor 39, and excessive propulsion force is generated in the direction of the arrow D11, the moment in the direction of the arrow D13 also increases, resulting in a state in which the meshing of the tooth component 43 and the lead screw 38 is irregular.
This irregular state is suppressed by limiting displacement with the tooth component thrust limiting member 46 when the tooth component 43 comes into contact with a limiting face 46A or limiting face 46B. This keeps the meshing in a regular state.
However, when the optical head 34 is subjected to an excessive external force, such as impact force, in its movement direction, the tooth component 43 may come out of the groove of the lead screw 38, so that the engagement cannot be maintained, even though the tooth component 43 is restricted in its displacement in the movement direction by the tooth component thrust limiting member 46. Consequently, the optical head 34 may move in an unrestricted state to the limit of its movable range in this direction, and collide with the inner peripheral stopper 32A or the outer peripheral stopper 32B at the innermost peripheral location or outermost peripheral location, respectively. A problem at this point is that the constituent members of the optical head 34 or the places where it is joined are susceptible to being damaged.
To solve this problem, the structure aimed at preventing the tooth component 43 from coming out of the groove of the lead screw 38 has been disclosed in Japanese Laid-Open Patent Application 2000-339882, for example. This structure will now be described through reference to FIGS. 19 and 20.
In FIG. 19, 12 is a turntable on which a disk (not shown) is placed and fixed. The turntable 12 is rotationally driven by a spindle motor 11. The chucking member for fixing the disk is not shown in FIG. 19. 16 is an optical head for recording on or reproducing from a disk by emitting a light beam, 13 and 14 are guide shafts for guiding the optical head 16 in the radial direction of the disk placed on the turntable 12. 22A, 22B, 22C, and 22D are bearings that support the guide shafts 13 and 14. 17 is a movement motor that serves as a drive source for moving the optical head 16 in the radial direction of the disk placed on the turntable 12, 15 is a lead screw comprising a spiral groove provided around the axial peripheral face of a shaft thereof and which is rotated by the drive force of the movement motor 17, 18 is a power transmission member that engages with the lead screw 15 and transmits a propulsion force that moves the optical head 16 in the disk radial direction, and 19 is a chassis that integrally supports the above-mentioned members.
With the structure shown in FIG. 19, when the movement motor 17 is driven, it moves the head 16 in the disk radial direction, and recording or reproduction is performed at a specific radial position of the disk.
FIG. 20 is a diagram of a state in which the power transmission member 18 and the lead screw 15 have been engaged. The power transmission member 18 is made up of an engagement component 20 provided with a tooth component 20A that fits into a spiral groove 15A of the lead screw 15, and a limiting component 21 for preventing the tooth component 20A from coming out of the spiral groove 15A.
Providing the limiting component 21 avoids the problem in which the engagement component 20 is displaced perpendicularly to the movement direction and the tooth component 20A comes out of the spiral groove 15A when the head 16 is subjected to an excessive movement force caused by impact or the like in the movement direction. This makes it possible to prevent the power transmission member 18 from being in an unrestricted state in the movement direction. This also prevents a situation in which, if the head 16 should be subjected to an impact force in its movement direction, the head 16 moves in an unrestricted state up to the limit of its movable range in the movement direction, collide with the base member 10 itself or one of the parts that are constituted integrally with the base member 10, and the constituent members of the head 16, or places where it is joined, are subjected to damage.
Patent Document 1: Japanese Laid-Open Patent Application H10-74370
Patent Document 2: Japanese Laid-Open Patent Application 2000-339882